This invention is related to visual display devices. It is particularly directed toward an improved gas discharge display for use in flat panel television, alpha-numeric displays and the like.
Gas discharge displays generally include a matrix of rows and columns of individual gas discharge cells. Typically, there are corresponding matrices and rows of columns of wire conductors which intersect at the individual cell locations. Each cell has at least an anode conductor and a cathode conductor between which a low pressure atmosphere of a gas, such as a rare gas or a rare gas and mercury vapor, is maintained. When a sufficient potential is applied between an anode conductor and a cathode conductor, a gas discharge is developed at the cell which is located at their intersection. A visible "cathode glow" is then established near the cathode and, in some applications, it is that glow which is used as the visible light output of the cell.
Between the anode conductor and the cathode glow a plasma or "positive column" may exist which includes energetic electrons, metastables and ions. These particles are continuously recombining, regenerating and colliding. The collision of an energetic electron with a gas atom produces a high energy state in the atom's electron shell which decays to a lower energy state, thereby causing an emission of radiation from the atom and from the positive column. The gas constituents and the operating parameters of a cell may be chosen such that the radiation emanating from a positive column is in the UV (ultraviolet) spectrum. The UV radiation may then be converted into visible light of a predetermined color by directing the UV radiation onto a UV-excitable phosphor coated on one or more of the cells walls.
When excited by the UV radiation, the phosphor coating emits visible light of the predetermined color. It is with this mode of generating visible light from a gas discharge cell that this invention is primarily concerned, although certain aspects of it are also applicable to applications utilizing only the cathode glow as the source of light output, as well as to applications where light is produced by direct electron excitation of a phosphor.
In the past, gas discharge displays have suffered from a number of problems, one which has been the high voltage required to drive the anode conductors in order to establish a discharge in selected cells. In typical commercial applications, anode conductors are driven with a potential of several hundred volts, generally in the form of a time-varying signal which corresponds to video information. In a television application, a typical gas discharge panel will have several hundred anode conductors, one for each column of the panel, and each driven by a video driver. To implement the circuitry required for such a system would be prohibitively expensive unless the circuitry could be realized in integrated circuit (IC) form. Since present IC technology is, for the most part, limited to the production of circuitry capable of handling less than 150 volts, the video drivers can probably not be profitably integrated at this time. Instead, a discrete high voltage video driver is probably required for each anode conductor. A display incorporating discrete video drivers for each anode conductor would obviously be too expensive for consumer applications.
Another problem which has been associated with many flat panel displays is the complexity of the display. Some displays are constructed of many layers which must be accurately aligned with one another. This type of construction is undesirable from a production standpoint, particularly where the final product is intended for the mass consumer market.
A flat panel display which is intended to be a consumer product should, therefore, incorporate a solution to the problem of needing hundreds of discrete video drivers, without increasing, and hopefully decreasing, the customary complexity of prior art displays.